Closed suction drains reduce postoperative hematoma formation, but create an entry portal for bacteria and thus increase the risk of infection. This study attempts to establish when the risks of wound drainage outweigh the benefits. In a prospective clinical trial, wound drains were used in all patients having a total knee or total hip arthroplasty. Timing of drain removal and amount drained were recorded. Drain-site swabs were sent with drain tips for bacteriology. Results suggest that the likelihood of bacterial colonization increases while wound drainage decreases with time. The authors conclude that the optimal time to remove drains is 24 hours after total joint arthroplasty.